When animal ear tags were first developed, the best available tag material was metal. To minimize snagging and consequently, loss of ear tags, the metal tags were made very small. Since the tags were small, they were very difficult to read and usually could only be read by restraining the animal. A typical metal ear tag is shown in Burgess U.S. Pat. No. 1,011,911. Although the small metal tags provided less of an area to snag, they were not resilient so if snagged, they would usually tear free from the ear.
With the advent of plastics, the metal tags began to be replaced by larger and more resilient plastic tags. One such prior art tag is shown in Ritchey U.S. Pat. No. 3,552,051. The Ritchey one-piece flexible plastic ear tag was made of polyurethane, resisted snagging, had large, easy-to-read numbers, and permitted adding color as an added identification feature. The one-piece flexible tags were applied with a knife-like applicator which required a certain amount of practice before the operator could quickly apply the one-piece ear tag. Although ear tag loss was greatly reduced with one-piece flexible tags, consumers preferred the use of plier-like applicators to apply two-piece animal ear tags since it required less skill to learn how to apply a flexible or resilient two-piece tag with a plier-like applicator.
Somewhat prior to and during the development of the flexible one-piece tags, nonflexible two-piece tags, partially flexible tags and flexible two-piece tags with a hard earpiercing tip were also developed. The two-piece flexible tags have generally received greater consumer acceptance since they were installed with a plier-type applicator which required little time or skill to operate.
Early models of plastic tags included a flexible, usually polyurethane identification panel with a boss end and a rigid plastic male button for piercing the ear and holding the identification panel in place by the boss. Such an animal ear tag is shown in Hayes U.S. Pat. No. 3,260,007.
It is commonly known that retention of tags with a flexible panel and rigid stud is not as good as retention of flexible one-piece tags because the rigid button often snags and tears free from the ear. Stud improvements helped to solve this problem through the development of a resilient stud that is applied with a plier that has an ear-piercing pin extending from the jaw. An example of such a stud is shown in Goldberg's South African application No. 64/2254 filed May 6, 1964 and Murphy, et al. U.S. Pat. No. 3,741,414. The Murphy, et al. U.S. patent shows the combination of a resilient stud and a flexible panel. Although snagging problems and consequently primary ear tag loss was reduced with the all-flexible tags made of polyurethane, we have discovered the secondary tag losses caused by polyurethane deterioration from exposure to such elements as UV light, chemicals, fungus and bacterial remained a problem. Nevertheless, of all ear tag materials available today, polyurethane is still considered by most tag manufacturers and producers to be the best material available for manufacturing tags that have minimal field loss.
One of the reasons flexible polyurethane ear tags minimize ear tag loss is due to the flexibility of the tag which permits the tag to bend and flex thus avoiding snagging on objects. For example, when animal ear tags are inserted in an animal's ear, the ear tag irritates the ear, causing the animal to rub the ear against an object which often results in dislodging the ear tag. If the tag is flexible, it will usually not snag since the tag will flex rather than snag.
While the all-flexible tags made from polyurethane have been found to minimize snagging problems associated with the animal rubbing its ear, we have also discovered the polyurethane material used to make such tags will, after extended use, begin to break down after prolonged exposure to bacteria and sunlight. In addition, cuts in the ear tag from barb wire will accelerate the loss problem. Typically, anywhere after a year of use we observed that some of the all-flexible polyurethane ear tags were beginning to fall off.
Observations of polyurethane tags that have been lost after field use of a year or more shows deterioration of the male studs most often occurs at the base of the shaft with the stud. This junction of the shaft with the stud flange is usually the weakest point of the tag, and the point where the tags receive the most stress if snagged. This junction is also more susceptible to being cut by barb wire.
In order to minimize these secondary losses due to polyurethane deterioration, it would be desirable to replace the polyurethane with another material that is less susceptible to long term deterioration, based on evolution of studs from hard material to studs made of more flexible material. It seemed unlikely that one could use harder materials that were resistant to breakdown and still have minimal initial ear tag loss.